We developed a coding scheme for this analysis through a preliminary examination of the transcripts, and by modifying the coding schemes for classroom discourse from our previous work. The coding scheme examined multiple aspects of classroom discussions: teachers’ use of academically productive talk moves (APT moves) to guide students’ reasoning; students’ attempts at co-co-constructing science understandings with peers; and students’ attempts at reasoning about the science.

We coded teachers’ turns at talk for the following talk moves.

Teachers’ Facilitation of Science Discussions:

• a.  Expand Moves (Say More, Revoice, Time to Think) (e.g., “Okay. Can you say a little more about that?”; “So you think the amount of space these take up depends on the room that they’re in or the house that they’re in?”; “Let’s all take a minute to think about that”)
• b.  Listen Moves (Who can Restate/Repeat) (e.g., “Can someone repeat what Avery said in their own words?”)
• c.  Dig Deeper Moves (Press for Reasoning/Why, Challenge) (e.g., “What is your evidence?”; “How do you know it didn’t rise? Did you measure it?”)
• d.  Think With Others (Add On, Who Can Explain, Do you Agree/Disagree) (e.g., “Oh! Hmm..What do we think? Anyone want to, maybe want to revise Mario’s idea, maybe change it, add to it?”; “What do we think that means? What do you think Amalia means when see says it causes physical breakdown?”; “Anyone disagree with that?”)

We coded students’ turns at talk for the following attempts at co-constructing ideas with their peers, and at reasoning about the science.

Students’ Co-construction Moves:

1. Agree (e.g., “I kind of agree with Daniel, because when you’re going to kick a soccer ball of course if it’s deflated you can’t really kick it that far.”)
2. Disagree (e.g., “No. But I disagree with what Daniel said with the salt being hot.”)
3. Ask for Clarification (e.g., “What do you mean when you say..?”)
4. Clarify Other (e.g., “I think what Shareen is trying to say, the water might dissolve into the salt and the salt might get dissolved, so the water level might go down a little bit.”)
5. Challenge (e.g., “But aren’t you pumping hot air into the ball? Because if you blow up, like a balloon, sometimes you pump in hot air and after that it starts making it rise kind of, and after that.”)
6. Add-On (e.g., “Um I also wanted to add on to Louie’s..”)
7. Restate Other (e.g., “She said there’s more space in the air particles. I mean when the particles are pushed like — yeah, pushed.”)

Students’ Reasoning:

Sense-Making Attempts: This category captured students’ efforts at making sense of the science.

1. Revise their own thinking (e.g., “Yeah, I agree that it’s Lela. Because after the — well, at first I thought it was Fern because I didn’t know that air had weight. Then after my education, I learned that Lela is probably correct.”).
2. Raise a related question (e.g., “I have a question. Where does the water go when it evaporates?”).
3. Propose test/thought experiment (e.g., “When Christiani said that if you put a cup and air in, but we’re not talking about a cup, we’re talking about a ball. So, if you have a scale and we fill it up with air, and it would not stay on zero. It would go — it would, um, go out between two, three — “).

Reasoning With Core Science Ideas: This category captured instances of students’ reasoning by drawing on core science ideas (classroom science investigations and scientific principles from the curriculum).

1. Reference to Classroom Science Investigations — Students referred to quantitative data and/or observations from previous and/or present science curriculum units (e.g., “Yeah. And they weighed the same, but then we kept one of the balloons not inflated and then we blew up the other one. And when we put it on that side was a little farther down, so that means it was heavier when it had air in it.”).
2. Reference to Scientific Principles (Principles such as air is matter; matter has weight and takes up space; the particulate nature of matter, etc.) - Students referred to scientific principles, ideas from the particle model (e.g., “I respectively disagree with Kiaja because I do think air has weight and that I agree with Layla and that the inflated soccer ball weighs more than the flat one. “).

Reasoning Without Core Science Ideas: This category captured instances where students drew on ideas outside of formal scientific understandings.

1. Reference to Outside Experience — Students described experiences from everyday life (e.g., “I think that Tomas is right, because it’s the same. I don’t have a soccer ball, but I do have a football. And, when the football gets flat, it is heavier. But, um, but when, um, air goes into the soccer ball, um, it makes it lighter because of all the gravity around”).
2. Presenting Assertions/Opinions — These were instances where students presented assertions that were either opinions or facts that may have been accurate or inaccurate with respect to canonical science (e.g., “Well, Claire is the most right, but the soccer ball would probably be a little heavier, because air is like .000000000001 more heavier, and the flat ball is the same exact thing as the actual soccer ball, but it just doesn’t have any air in it, so it’s pretty much the same.”).
3. Analogy — This code captured instances where students drew similarity to other hypothetical situations (e.g., “ I have something- I agree with Ryan because if you take an air mattress out it would feel heavy and then when you blow it up it would feel easier to carry and lighter.”).
4. Logical Train — This code captured “if...then” statements expressing axiomatic reasoning and counterfactual thinking (e.g., “But if you think that the air has weight, like if it adds weight to it, then if you put a scale in the middle of the room right here there would probably be at least a pound showing on it.”).